In a Long Term Evolution (LTE) wireless communication system, a User Equipment (UE) may trigger a Scheduling Request (SR) procedure to request the network to allocate uplink radio resources for transmission when certain SR triggering condition(s) is satisfied. For example, if the UE has no uplink radio resources for transmitting the Buffer Status Report (BSR) Medium Access Control (MAC) Control Element (CE), or does not receive a positive feedback (e.g., allocation of uplink radio resources for transmission) of the BSR from the base station, the UE may trigger the SR procedure. Furthermore, once the SR procedure has failed, a Random Access (RA) procedure will be triggered, such that the pending SR procedure is cancelled.
For the next generation (e.g., 5G New Radio (NR)) wireless communication technology, the UE's Medium Access Control (MAC) entity can be configured with zero, one, or more than one SR configuration by a base station (e.g., next generation NodeB (gNB)). Each SR configuration may correspond to one or more Logical Channels (LCHs), and each LCH may be mapped to zero or one SR configuration. If a UE triggers an SR procedure for an LCH configured with an SR configuration, the UE may use the SR configuration to perform the SR procedure, which includes the SR transmission via the uplink radio resource indicated by the SR configuration. That is, the SR configuration of the LCH that triggers the BSR may be considered as the corresponding SR configuration for the triggered SR procedure. However, the SR operation for the LCH with zero SR configuration is still an open issue.
Thus, there is a need in the art for an adaptive SR procedure for LCH(s) configured with zero SR configuration in the next generation wireless communication system.